Saw-tooth multivibrator circuit



Jan. 2, 1951 F. H. SLAYMAKER ETAL 2,536,822

SAW-TOOTH MULTIVIBRATOR CIRCUIT Filed April 15, 1946 UOUJP w-{III I L/|o LOAD l 3 g INVENTORS 4 WILLARD F. MEEKER BY FR-ANK H. SLAYMAKER jizzzz TORNEYS Patented Jan. 2, 1 951 Frank H. Slaymaker and Willard F.Meeker,

Rochester, N. Y., assignors to Stromberg-Carlson Company, Rochester, N.Y., a corporation of New York Application. April15, 1946, Serial No.662,144

5 claims; (01. 250-36) l This invention relates to wave generators andmore particularly to means for generating sawtooth waves.

Circuits have heretofore been devised for producing or generating waveshaving a saw-tooth configuration. For example, blocking oscillators havebeen used frequently for this purpose but relatively high voltage plateor anode supplies are required. i

It is an object of this invention'to provide a new and improved. meansfor producing a sawtooth wave i using a minimum numberof parts, having alow cost, which is light in weight and which enables use of electrondischarge devices utilizing low current filamentsand relatively lowanode voltages. r l

It is another object of this invention to employ a multivibrator circuitto produce saw-tooth Waves. This object is achieved by making .thevalues of resistance and capacitance associated with the anodes of themultivibrator. tubes. of such values that the time constant thereof isrelatively long.-

Other objects and advantages of this. invention will become apparent asthe following description proceeds when read with reference to theaccompanying drawing in which Fig. 1 is a circuit diagram illustratingan embodiment of. the invention, Fig. 2 comprises a series of diagramsuseful to a complete understanding of the operation, of the circuit ofFig. 1, and Fig. 3 is a modification of the circuit shown in Fig. 1.

Referring to Fig. 1, there is shown a multivibrator comprising a pair ofelectron discharge devices I and 2 including anodes 3 and 4,respectively, filaments 5 and 6 respectively; and control electrodes 1and 8 respectively. The operating current supply includes a suitablesource ofpotential 9 whose negative terminal is grounded and whosepositive terminal is connectedto anodes 3 and 4 through suitableresistances 1 and il as shown. .The filaments 5 and 6 are grounded inthis embodiment of our invention. The control electrodes 1 and 8 arepositively biased by means of a connection to the source of potential 9throughresistors l2, .l3 and M as shown, the resistor [2 being common toboth biasing circuits and preferably being variable to enable easyadjustmentof the bias and hence of-the frequency of oscillation. Inorder to cause the discharge devices to operate inmultivibratoiigfashion, a condenser L5 :is connected betweenco'ntrolelectrode 1 and anode 4 and a condenser is connected between control.electrode a'and anode 3.

As :iswellunderstood. in customary -multiyi--zbrator circuits, there areperiodically produced at .the anodes substantially square pulses. Thiscondition is illustrated in Fig. 2 wherein at A is depicted thepotentials appearing at one of the anodes (let us assume anode 3) and atB is illustrated the potentials existing at the other anode (anode 4) atthe same instants of time.

In accordance with our invention the capacitance of capacitors I5 andI6, and the resistance of resistor H are so chosen that the anode andcontrol-electrode potentials change so slowly that the control electrodeincreases in the positive sense to cut-oil? while the anode potential isstill increasing linearly. In Fig. 2, at C and D are representedpossible potentials at control-electrodes 1 and 8 respectively varyingwith time. Cut-off is represented by the dashed line. At E and F of Fig.2, possible potentials of anodes 3 and 4 are shown. The dotted linesrepresent the potential relationship if the multivibrator period is longenough to permit the potential to reach its maximum. In accordance withthe conditions set jorth above, however, at time 131 for example, thecontrol electrode of discharge device I reaches ,cut-off and device Iconducts. During the rise ,of potential at control-electrode I (Fig.20), the anode potential is increasing as shown at Fig. 2E. Thepotential at control-electrode 8 now begins to rise toward cut-off (Fig.2D) and at time its the multivibrator again switches. Figs. 2E and .21therefore show that saw-tooth pulses of voltage appear alternately atthe anodes. In other words, the R-C, or time constants, of the anode.circuits are so chosen that the anode potential rises linearlythroughout the non-conducting or .ofi period of each discharge device.The anodes :may be connected through suitable resistance .means whichmay be a single tapped resistor, a potentiometer, or two separateresistors, one end of each being connected to an anode and the otherends connected to load resistor III. In Fig. -1 there is illustrated apotentiometer ll. .3 shows the use of two resistances l8 and I9. A ,loadI! connected across resistor ill will have Fig.

supplied to it a saw-tooth wave of form illus- ,trated by Fig. 2G.

Use of a potentiometer facilitates balancing of the circuit to insurelikeness of successive saw-teeth.

In Fig. 3 there is shown a modification elimiv nating the potentiometerH. In this arrangement anodes 3 and 4 are connected to the endsofresistors 18 and [9 respectively, and the common connection between theresistors is connected to the positive terminal of source 9 throughresistor I0.

To illustrate suitable parameters for the practice of our invention,referring to Fig. 3, satisfactory results have been obtained using typeCKEOQAX discharge devices, resistances I3 and 14 of one megohm each,resistances l8 and I9 of 0.47 megohm each, resistance In of 0.1 megohmand capacitors l and i6 of 0.3 microfarad each.

The frequenc of the generated wave is controlled by adjusting thecontrol-electrode potentials by means of resistance E2. The minimumfrequency while maintaining linearit is determined by the time duringwhich the anode potential rises linearly.

While we have shown and described a particular embodiment of ourinvention, it, will be. obvious to those skilled in the art that changesand modifications may be made without departing from our invention inits broader aspects. For example, heater tubes may be substituted forfilament devices l and 2. We, therefore, aim in the appended claims tocover all such changes and modifications as fall within the true spiritand scope of our invention.

What we claim is: y 1. A saw-tooth wave generator including amultivibrator comprising a pair of electron discharge devices eachhaving a cathode, an anode and a control electrode, a connection joiningsaid cathodes, continuously conductive means for biasing said controlelectrodes, cross-couplings between the anode of one of said devices andthe control electrode of the other of said devices and l riods.

2. A saw-tooth wave generator including a" 'multivibrator comprising apair of electron discharge devices each havin a cathode, an anode and acontrol electrode, a connection joining said cathodes, continuouslyconductive means for biasing said control electrodes comprisingresistive elements connected to a source of positive potential, thenegative terminal of said source being jconnected to said connectedcathodes, crosscouplings between the anode of oneof said devices and thecontrol electrode of the other of said devices and between the controlelectrode of said one device and the anode of said other device, tapp-edresistance means connected between said anodes, a resistance elementconnected in series between said source of positive potential and thetap on said resistance means, and a load element connected across aportion of said resistance element, said cross-couplings and resistance;means being chosen to provide a time constant 'sufliciently great tocause the anode potential of each discharge device to rise substantiallylinear- "ly throughout its own non-conducting periods.

3. A saw-tooth wave generator includin a multivibra tor comprising apair of electron disj charge devices each having a cathode, an anode anda control electrode, a connection joining said 4 cathodes, continuouslyconductive means for biasing said control electrodes, cross-couplingsbetween the anode of one of said devices and the control electrode ofthe other of said devices and between the control electrode of said onedevice and the anode of said other device, tapped resistance meansconnected,- between said anodes, a source of direct-current potentialand a resistance element connected in series between said connectedcathodes and the tap on said resistance means, the negative terminal ofsaid source being connected to said connected cathodes, and a loadelement connected across a portion of said resistance element, saidcross-couplings and resistance means being chosen to provide a timeconstant sufiiciently great to cause the anode potential of eachdischarge device to rise substantially linearly throughout its ownnon-conducting periods.

4. A saw-tooth wave generator including a multivibrator comprisin a pairof electron discharge devices each having a cathode, an anode and acontrol electrode, a connection joining said cathodes, individualresistive means for biasing each of said control electrodes,cross-couplings between the anode of one of said devices and the controlelectrode of the other of said devices and between the control electrodeof said one device and the anode of said other device, tapped resistancemeans connected between said anodes, a source of potentialand aresistance: element connected in series between 'said:connected cathodesand the tap on said resistance means, and a load element connectedacross a portion of said re* sistance element, said cross-couplings andresistance means being chosen to provide a time constant sufiicientlygreat to cause the anode poten- 'tial of each discharge device to risesubstantially linearly throughout its own non-conducting periods.

5. A saw-tooth wave generator including a multivibr'ator' comprising apair-of electron discharge devices, each having a cathode, an anode, anda control electrode, a'connection joining said cathodes, crosscouplings-between the anode of one of said devices and the controlelectrode of the other of said devices and between the control electrodeof said one device and the anode of said other device, each of saidcross couplings including a capacitorya source of anode potential, a

connection between the positive terminal of said source of potential andeach of said anodes including resistance means common to both anodecircuits, and an output circuit connected across a portionofisaid commonresistor, the capacitance of eachof said capacitors and the resistanceof said resistance means being chosen to provide a time constantsufficiently great to cause the anode'potential'of each discharge deviceto rise substantially linearly throughout its own nonconducti'ngperiods. I FRANK H. 'SLAYMAKER.

' WILLARD F. MEEKER;

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Morton et al.v Oct. 22, 1946

